Revert "Resolve "Veranstaltungshierarchie: Fehler beim Anlegen von Unterelementen""

This reverts commit 704d702b.

app/controllers/admin/tree.php

@@ -130,15 +130,12 @@ class Admin_TreeController extends AuthenticatedController
         $node->parent_id = Request::option('parent_id');
 
         $parent = $classname::getNode(Request::option('parent_id'));
-        $children = $parent->getChildNodes();
-        $maxprio = !empty($children)
-            ? max(array_map(
-                function ($c) {
-                    return $c->priority;
-                },
-                $children
-            ))
-            : 0;
+        $maxprio = max(array_map(
+            function ($c) {
+                return $c->priority;
+            },
+            $parent->getChildNodes()
+        ));
         $node->priority = $maxprio + 1;
 
         if (Request::option('studip_object_id')) {